Tail gas treatment method and system and application

Abstract

The invention discloses a tail gas treatment method and system and application. The method comprises the following steps: mixing a tail gas material flow and a jet liquid material flow in a liquid jet vacuum pump, and then feeding into a separator; after the tail gas material flow is mixed with the jet liquid material flow, the tail gas material flow is cooled but not condensed; separating a second gas material flow and a second liquid material flow from the separator, condensing the second gas material flow, dividing the condensed second gas material flow into a third gas material flow and a third liquid material flow, and returning the third liquid material flow to the separator; the second liquid material flow and the third liquid material flow are mixed in the separator and then are conveyed to a conveying pump, a fourth liquid material flow at an outlet of the conveying pump is divided into two parts, one part serves as a jet flow liquid material flow to be conveyed into the liquid jet flow vacuum pump, and the other part is extracted. According to the method, energy coupling and material recycling of the whole system are considered, the technical target of long-period operation of the device is achieved under the conditions of short process and less equipment, and meanwhile, the method has the advantages of low energy consumption and low material consumption.

Description

Technical Field

[0001] The present invention relates to the technical field of tail gas treatment. Further, it relates to a method and system for tail gas treatment and applications. Background Art

[0002] Polymer polyol (POP) is based on general polyether polyol, added with acrylonitrile, styrene and initiator azobisisobutyronitrile for free radical graft polymerization. During the production process, solvents such as isopropanol also need to be added as chain transfer agents. There will be a certain amount of monomer residues in the final product. The small molecule monomers remaining in the polymer polyol will increase the odor of the polymer polyol product, and the remaining solvents such as isopropanol will also affect the product performance of the product. In order to obtain polymer polyol with low residues, polyether production enterprises need to bubble and then vacuum remove the unreacted monomers and isopropanol that do not participate in the reaction during the reaction process through a flash tank. However, in the prior art for treating the above-mentioned tail gas, a steam jet pump is used to extract the tail gas in the vacuum device, and then a large amount of cooling water is used to condense the tail gas. However, since the temperatures of both the steam and the tail gas are very high, and since the tail gas contains unsaturated bond high-temperature gases, it is easy to self-polymerize and block pipelines and equipment during transportation, thus affecting the long-term operation of the device. Therefore, it is necessary to develop an effective method for treating tail gas to avoid blockage of the pipeline by the tail gas.

[0003] In addition, an ejector is a fluid power pump. A fluid power pump has no mechanical transmission and mechanical working components. It uses the energy of another working fluid as a power source to transport low-energy liquids and is very safe for sucking flammable and explosive materials. An ejector is a device that uses a high-speed jet passing through a nozzle to extract the gas in a container to obtain a vacuum, also known as a jet vacuum pump. In petrochemical industry production, it is often used for the purpose of creating a vacuum.

[0004] Common types of ejectors include steam ejectors, air ejectors, and water ejectors.

[0005] A steam jet pump uses steam as the working medium and is a jet vacuum pump that can directly exhaust to the atmosphere. This pump starts quickly, occupies a small area, has a wide working pressure range, a large gas extraction volume, and can extract gases containing dust, corrosive substances, flammable and explosive gases. The disadvantages of this pump are high civil engineering investment and large cooling water consumption.

[0006] An air ejector uses compressed air or atmospheric air as the working medium. It relies on the low pressure generated by the air flow at the nozzle outlet to suck air or other gases and then compress and discharge them. According to whether the working medium is high-pressure air or atmospheric air, it is divided into a general air ejector pump and an atmospheric ejector pump. The working medium consumption of an air ejector pump is large, and a large-capacity air compressor must be available.

[0007] A water ejector uses water as the working fluid in a water jet pump to generate a vacuum and is suitable for occasions with not too high a vacuum degree. It belongs to a rough vacuum device.

[0008] Patent CN204540791U discloses a vacuum pumping device. Its purpose is to provide an environmentally friendly and energy-saving vacuum device, as much as possible reducing the noise generated by the vacuum system and preventing the pollution of the surrounding environment by the peculiar smell and waste water generated during the tobacco vacuum conditioning process. An environmentally friendly and energy-saving vacuum device of the present utility model includes a vacuum box body, a steam jet pump assembly, an air jet pump assembly, a water delivery pump assembly, a water-soluble tank, a spray condenser, an absorption purifier, a cooling assembly, and a circulation water tank. The air inlet and the exhaust port of the spray condenser are respectively communicated with the exhaust port of the steam jet pump assembly and the suction port of the air jet pump assembly. The water outlet of the spray condenser is connected to the water inlet of the absorption purifier. The water outlet of the absorption purifier is communicated with the water inlet of the cooling assembly. The water outlet of the cooling assembly is communicated with the water inlet of the circulation water tank. The water outlet of the water-soluble tank is communicated with the circulation water tank. The water outlet of the circulation water tank is respectively connected to the water inlet of the spray condenser and the water inlet of the water delivery pump assembly.

[0009] The inventors of the present invention found that existing articles and patent reports of water ejectors (such as ejectors with a Venturi-like structure) are mostly used for vacuum pumping, or the jet liquid is recycled to the ejector after cooling. The inventors of the present invention found that there is less consideration for simultaneously achieving the functions of vacuum pumping and cooling the vacuum gas, especially in terms of the energy coupling of the entire system and the recycling of materials. Summary of the Invention

[0010] To solve the problems in the prior art, the present invention proposes a method, a system and an application for tail gas treatment. In the tail gas treatment process of the present invention, the steam ejector pump in the prior art is replaced by a water ejector (i.e., the liquid jet vacuum pump of the present invention), and the energy coupling of the whole system and the recycling of materials are considered. The involved process flow is as follows: first, it is mixed with the jet liquid in the liquid jet vacuum pump for cooling instead of condensation, and at the same time, the functions of vacuum pumping and gas cooling are achieved, avoiding the self-polymerization of substances containing unsaturated bonds; after gas-liquid separation inside the separator, the gas is further sent to the condenser for condensation. After a large amount of high-boiling substances are condensed here, the condensate is sent to the separator and mixed with the jet liquid circulating inside the separator to achieve the effect of cooling the jet liquid. The jet liquid does not need to be provided with a separate condenser device. As time accumulates, the liquid level inside the separator will gradually rise. Therefore, it is necessary to take out at the outlet of the transfer pump to balance the system. It can be seen that the tail gas treatment process of the present invention adopts a multi-stage treatment scheme for high-temperature tail gas containing unsaturated bonds, effectively realizing the cooling treatment of the tail gas, and at the same time realizing the energy coupling of the whole system and the recycling of materials; effectively solving the problems that the high-temperature tail gas containing unsaturated bonds in the polyether industry is prone to self-polymerize and block pipelines and equipment, thus affecting the long-term operation of the device, and the existing steam ejector requires a large amount of cooling water consumption.

[0011] One of the purposes of the present invention is to provide a method for tail gas treatment, including the following steps:

[0012] a) Mix the tail gas stream and the jet liquid stream into the liquid jet vacuum pump and then enter the separator; wherein, the gas in the tail gas stream includes gas containing unsaturated bonds; after the tail gas stream is mixed with the jet liquid stream, the tail gas stream is cooled but not condensed;

[0013] b) Separate the second gas stream and the second liquid stream from the separator, condense the second gas stream, and after condensation, it is divided into the third gas stream and the third liquid stream, and return the third liquid stream to the separator;

[0014] c) The second liquid stream and the third liquid stream are mixed in the separator and then sent to the inlet of the transfer pump. The fourth liquid stream at the outlet of the transfer pump is divided into two streams. One stream is sent as the jet liquid stream into the liquid jet vacuum pump, and the other stream is sent out of the system as the extraction stream.

[0015] The technical solution of the present invention mainly lies in cooling the tail gas and avoiding the problem that the high-temperature tail gas containing unsaturated bonds is prone to self-polymerize and block the pipeline. The second gas stream generated in the system of the present invention and one extraction stream separated from the fourth liquid stream can be further processed according to the prior art, or some components therein can be further recovered according to production needs.

[0016] In the method for tail gas treatment described in the present invention, preferably,

[0017] Step a),

[0018] The unsaturated bond in the gas containing unsaturated bonds refers to C═C, and / or C≡C, and / or C≡N; preferably, the gas in the tail gas stream includes acrylonitrile, and / or styrene, and / or isopropanol gas; preferably, in the tail gas stream, the volume ratio of the gas containing unsaturated bonds is 2.0% to 18.0%, preferably 3.0% to 17.0%; and / or,

[0019] The pressure of the tail gas stream is 0.1 to 15.0 KPaA, preferably 0.1 to 12 KPaA; more preferably 0.1 to 10.0 KPaA; and / or,

[0020] The jet liquid stream mainly includes water, preferably the mass content of water is 94.0% to 99.9%, more preferably 95.0% to 99.9%.

[0021] In the method for treating tail gas according to the present invention, preferably,

[0022] Step a),

[0023] The temperature of the tail gas stream before entering the liquid jet vacuum pump is 110 to 210 °C, preferably 120 to 200 °C; and / or,

[0024] The mass flow ratio of the tail gas stream to the jet liquid stream is 1:(0.1 to 6.0), preferably 1:(0.15 to 5.5); more preferably, after the tail gas stream and the jet liquid stream enter the liquid jet vacuum pump and are mixed, the temperature of the tail gas stream is 10 to 60 °C, preferably 10 to 55 °C, more preferably 15 to 55 °C.

[0025] In the method for treating tail gas according to the present invention, preferably,

[0026] Step b),

[0027] The separator is a sealed container, and a vacuum pumping device is provided after the condenser for condensation. The vacuum pumping device sends the second gas stream to the condenser under negative pressure;

[0028] Preferably,

[0029] The pressure in the separator is 10.0 to 30.0 KPaA, preferably 10.0 to 25.0 KPaA; more preferably 10.0 to 20.0 KPaA.

[0030] In the technical solution of the present invention, the separator is a container without special internal components. After the tail gas stream and the jet liquid stream enter the liquid jet vacuum pump and are mixed, they enter the separator from the outlet. Due to the action of gravity, the gas and the liquid will naturally separate.

[0031] In the method for treating tail gas according to the present invention, preferably,

[0032] Step b),

[0033] The second gas stream is an uncondensed tail gas stream; preferably, by volume percentage, the second gas stream includes 28.00% - 48.00% water, 1.20% - 9.20% acrylonitrile, 2.70% - 22.70% isopropanol, and 24.40% - 44.40% styrene; and / or,

[0034] The second liquid stream is a condensed tail gas stream; preferably, by mass percentage, the second liquid stream includes 91.00% - 99.90% water, 10 - 4000 PPM acrylonitrile, 0.02% - 5.00% isopropanol, and 1 - 2000 PPM styrene.

[0035] In the method for treating tail gas according to the present invention, preferably,

[0036] Step b),

[0037] The temperatures of the third gas stream and the third liquid stream at the outlet of the condenser are each independently ≤ 40°C, preferably ≤ 20°C;

[0038] Preferably, by volume percentage, the third gas stream includes 7.00% - 27.00% water, 5.81% - 30.00% acrylonitrile, 0.10 - 10.10% isopropanol, and 41.80% - 81.80% styrene; and / or,

[0039] By mass percentage, the third liquid stream includes 27.70 - 47.70% water, 0.10 - 10.20% acrylonitrile, 2.50 - 23.40% isopropanol, and 24.00 - 68.40% styrene.

[0040] In the method for treating tail gas according to the present invention, preferably,

[0041] Step c),

[0042] The outlet pressure of the transfer pump is 0.2 - 1.0 MPaG, preferably 0.2 - 0.8 MPaG; and / or,

[0043] The temperature of the fourth liquid stream at the outlet of the transfer pump is 15 - 40°C, preferably 15 - 35°C.

[0044] A second object of the present invention is to provide a tail gas treatment system, comprising:

[0045] A tail gas raw material tank, a liquid jet vacuum pump, a separator, a condenser, a delivery pump and a vacuum pumping device; the discharge port of the tail gas raw material tank is connected to the gas inlet of the liquid jet vacuum pump; the discharge port of the delivery pump is connected to the liquid inlet of the liquid jet vacuum pump; the discharge port of the liquid jet vacuum pump is connected to the inlet of the separator; the liquid discharge port of the separator is connected to the inlet of the delivery pump; the gas discharge port of the separator is connected to the inlet of the condenser; the liquid discharge port of the condenser is connected to another inlet of the condenser; the vacuum pumping device is connected to the gas material flow pipeline of the condenser; the discharge port of the delivery pump is also connected to the material extraction pipeline;

[0046] Preferably, the tail gas treatment method described in one of the objects of the present invention adopts the system.

[0047] In the tail gas treatment system of the present invention, preferably,

[0048] The tail gas raw material tank is selected from vacuum containers, preferably a stirring device is provided in the vacuum container; and / or,

[0049] The liquid jet vacuum pump is an ejector with a Venturi structure; and / or,

[0050] The delivery pump is selected from at least one of a booster pump and a centrifugal pump.

[0051] In the technical solution of the present invention, the purpose of providing a stirring device in the vacuum container is to make it easier to remove the tail gas from the inside of the vacuum container.

[0052] In the technical solution of the present invention, the liquid jet vacuum pump is an ejector with a Venturi structure; the Venturi tube is a structural form that first constricts and then expands. The ejector with a Venturi structure adopted in the present invention uses the condensate pumped by the pump as power, which will generate a vacuum environment and suck in the incoming gas, so that the gas and liquid are mixed in the ejector.

[0053] In the tail gas treatment system of the present invention, preferably,

[0054] The discharge port of the liquid jet vacuum pump is located inside the separator, and the discharge port of the liquid jet vacuum pump is higher than the maximum height of the liquid level inside the separator.

[0055] A third object of the present invention is to provide an application of the tail gas treatment method described in one of the objects of the present invention or the tail gas treatment system described in the second object of the present invention in the tail gas treatment of polyether production.

[0056] The main concept of the technical solution adopted by the present invention is as follows:

[0057] In the technical solution of the present invention, a multi-stage treatment scheme is adopted for the high-temperature tail gas containing unsaturated bonds. First, it is mixed with the jet liquid in a Venturi ejector for cooling instead of condensation, and the temperature is quickly reduced to below 60°C, preferably to 50°C, so as to avoid the self-polymerization of substances containing unsaturated bonds. After gas-liquid separation inside the separator, the gas is further sent to a condenser for condensation. Generally, it is condensed to below 40°C here, preferably to below 20°C. After a large amount of high-boiling substances are condensed here, the condensate is sent to the separator. In the present invention, due to the reason of pressure balance, the condensate can be sent to the separator by gravity flow, and after mixing with the circulating jet liquid, it can play a role in cooling the jet liquid. There is no need to separately set a condenser device for the jet liquid. As time accumulates, the liquid level inside the separator will gradually rise. Therefore, it is necessary to take measures at the outlet of the transfer pump to balance the system.

[0058] In the technical solution of the present invention, the materials and energy are coupled and utilized to achieve the technical goal of long-term operation of the device with a short process and few equipment, and at the same time, it has the advantages of low energy consumption and small material consumption.

[0059] In the ranges and any values disclosed in the present invention, the endpoints and any values of the ranges are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this article. In the following text, in principle, the various technical solutions can be combined with each other to obtain new technical solutions, which should also be regarded as specifically disclosed in this article.

[0060] Compared with the prior art, the present invention has at least the following advantages:

[0061] In the tail gas treatment process of the present invention, the steam ejector in the prior art is replaced by a water ejector, and the energy coupling and material recycling of the whole system are considered to achieve the technical goal of long-term operation of the device with a short process and few equipment, and at the same time, it has the advantages of low energy consumption and small material consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 It is a schematic diagram of the process system for tail gas treatment adopted by the present invention.

[0063] Figure 2 It is a schematic diagram of the process flow system adopted in Comparative Example 1.

[0064] Figure 1 、 Figure 2 MARKING DESCRIPTION:

[0065] 101. High-temperature gas stream containing unsaturated bonds

[0066] 102, Jet liquid stream

[0067] 103, Feed stream of transfer pump,

[0068] 104, Fourth liquid stream

[0069] 105, Product stream

[0070] 106, Second gas stream

[0071] 107, Third gas stream

[0072] 108, Third liquid stream

[0073] 202, Jet steam stream

[0074] 203, Outlet stream of ejector

[0075] 204, Fourth gas stream

[0076] 205, Fifth gas stream

[0077] 206, Fifth liquid stream

[0078] 207, Cooling water stream

[0079] 208, Bottom discharge stream of separator

[0080] 209, Another product stream

[0081] V1, Tail gas raw material tank

[0082] V2, Separator

[0083] J, Liquid jet vacuum pump

[0084] P, Transfer pump

[0085] E, Condenser

[0086] F, Vacuum pumping device

[0087] G, Gas jet ejector

[0088] Figure 1In it, the tail gas logistics (high-temperature gas logistics containing unsaturated bonds) 101 in the tail gas raw material tank V1 is sent to the liquid jet vacuum pump J under negative pressure. After being mixed with the jet liquid logistics 102 in the liquid jet vacuum pump J, it is sent to the separator V2 for natural separation, and is separated into the second gas logistics 106 and the second liquid logistics. The second gas logistics 106 is sent to the condenser E under the negative pressure generated by the vacuum pumping device F. After condensation, it is divided into the third gas logistics 107 (the third gas logistics is taken out of this system) and the third liquid logistics 108. The second liquid logistics and the third liquid logistics are mixed in the separator V2 to form the feed logistics 103 for the delivery pump, and are sent to the delivery pump P. The fourth liquid logistics 104 at the outlet of the delivery pump P is divided into two streams. One stream is sent to the liquid jet vacuum pump J as the jet liquid logistics 102, and the other stream is sent out of the system as the take-out logistics 105.

[0089] Figure 2 In it, the tail gas logistics (high-temperature gas logistics containing unsaturated bonds) 101 in the tail gas raw material tank V1 is sent to the gas jet ejector G under negative pressure. After being mixed with the steam logistics 202 in the gas jet ejector G, it is sent to the separator V2 as the ejector outlet logistics 203, and is separated into the fourth gas logistics 204 and the fourth liquid logistics. The fourth gas logistics 204 is sent to the condenser E under the negative pressure generated by the vacuum pumping device F. After condensation, it is divided into the fifth gas logistics 205 and the fifth liquid logistics 206. The fourth liquid logistics and the cooling water logistics 207 are mixed in the separator V2 to form the bottom discharge logistics 208 of the separator. The fifth liquid logistics 206 and the bottom discharge logistics 208 of the separator converge to form another take-out logistics 209 and are sent out of the system. Detailed implementation manners

[0090] The present invention will be specifically described below in conjunction with specific drawings and embodiments. It is necessary to point out here that the following embodiments are only used for further illustration of the present invention and cannot be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art to the present invention based on the content of the present invention still fall within the protection scope of the present invention.

[0091] In addition, it should be noted that the various specific technical features described in the following detailed implementation manners can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

[0092] In addition, any combination can be made between various different embodiments of the present invention as long as it does not violate the idea of the present invention. The technical solutions formed thereby belong to a part of the original public content of this specification and also fall within the protection scope of the present invention.

[0093] For the raw materials used in the examples and comparative examples, if not specifically defined, they are all disclosed in the prior art. For example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0094]

Example 1

[0095] As Figure 1 shown, the tail gas treatment system of the present invention includes: a tail gas raw material tank V1, a liquid jet vacuum pump J, a separator V2, a condenser E, a delivery pump P, and a vacuum pumping device F.

[0096] The discharge port of the tail gas raw material tank is connected to the gas inlet of the liquid jet vacuum pump; the discharge port of the delivery pump is connected to the liquid inlet of the liquid jet vacuum pump; the discharge port of the liquid jet vacuum pump is connected to the inlet of the separator; the liquid discharge port of the separator is connected to the inlet of the delivery pump, and the discharge port of the liquid jet vacuum pump is located inside the separator, and the discharge port of the liquid jet vacuum pump is higher than the maximum height of the liquid level inside the separator; the gas discharge port of the separator is connected to the inlet of the condenser; the liquid discharge port of the condenser is connected to the other inlet of the condenser; the vacuum pumping device is connected to the gas material flow pipeline of the condenser; the discharge port of the delivery pump is also connected to the material extraction pipeline;

[0097] Among them, the tail gas raw material tank is selected from a vacuum container, and a stirring device is provided inside the vacuum container; the liquid jet vacuum pump is an injector with a Venturi structure; the delivery pump is selected from a booster pump; the separator is a closed container.

[0098] The process flow of the tail gas treatment system of the present invention is as follows:

[0099] The tail gas stream 101 (a high-temperature gas stream containing unsaturated bonds) in the tail gas raw material tank V1 is sent to the liquid jet vacuum pump J under negative pressure (the negative pressure generated by the liquid jet vacuum pump), mixed with the jet liquid stream 102 in the liquid jet vacuum pump J, and then sent to the separator V2 for natural separation, and is separated into a second gas stream 106 and a second liquid stream; the second gas stream 106 is sent to the condenser E under the negative pressure generated by the vacuum pumping device F, and after condensation, it is divided into a third gas stream 107 (the third gas stream is extracted from the system) and a third liquid stream 108; the second liquid stream and the third liquid stream are mixed in the separator V2 to form a feed stream 103 for the delivery pump, which is sent to the delivery pump P. The fourth liquid stream 104 at the outlet of the delivery pump P is divided into two streams, one stream is sent as the jet liquid stream 102 to the liquid jet vacuum pump J, and the other stream is sent out of the system as the extraction stream 105.

[0100]

Example 2

[0101] A method for treating tail gas, using the tail gas treatment system shown in Example 1, includes the following steps:

[0102] a) The tail gas stream and the jet liquid stream enter a liquid jet vacuum pump for mixing, and then enter a separator; wherein, the gas in the tail gas stream includes gases containing unsaturated bonds; after the tail gas stream is mixed with the jet liquid stream, the tail gas stream is cooled but not condensed;

[0103] Among them, the gas in the tail gas stream is the tail gas generated during the removal of small molecule monomers during the flash evaporation of the crude product in polyether production, including acrylonitrile, styrene and isopropanol gases; preferably, in the tail gas stream, the volume ratio of the gas containing unsaturated bonds is 3.0%;

[0104] The pressure of the tail gas stream is 10 KPaA; the jet liquid stream mainly includes water, and the water content is 99.90%;

[0105] The temperature of the tail gas stream before entering the liquid jet vacuum pump is 120 °C; the mass flow ratio of the tail gas stream to the jet liquid stream is 1:0.2; after the tail gas stream and the jet liquid stream enter the liquid jet vacuum pump for mixing, the temperature of the tail gas stream is 54 °C.

[0106] b) A second gas stream and a second liquid stream are separated from the separator, the second gas stream is condensed, and after condensation, it is divided into a third gas stream and a third liquid stream, and the third liquid stream is returned to the separator;

[0107] Among them, the separator is a sealed container; a vacuum pumping device is provided after the condenser to send the second gas stream to the condenser under negative pressure; the pressure of the separator is 20.0 KPaA;

[0108] The second gas stream is an uncondensed tail gas stream; wherein, by volume percentage, the second gas stream is 39.67% water, 5.10% acrylonitrile, 12.19% isopropanol, 43.04% styrene; the second liquid stream is a condensed tail gas stream; by mass percentage, the second liquid stream is 97.83% water, 713 PPM acrylonitrile, 2.00% isopropanol, 361 PPM styrene.

[0109] The temperatures of the third gas stream and the third liquid stream at the outlet of the condenser are each independently 5 °C;

[0110] Among them, by volume percentage, the third gas stream is 15.93% water, 14.86% acrylonitrile, 4.55% isopropanol, 64.66% styrene; by mass percentage, the third liquid stream is 39.85% water, 5.03% acrylonitrile, 12.25% isopropanol, 42.87% styrene.

[0111] c) The second liquid stream and the third liquid stream are mixed in a separator and then sent to the inlet of a transfer pump. The fourth liquid stream at the outlet of the transfer pump is divided into two streams. One stream is sent as a jet liquid stream to a liquid jet vacuum pump, and the other stream is sent out of the system as a withdrawn stream;

[0112] Among them, the pressure at the outlet of the transfer pump is 0.2 MPaG; the temperature of the fourth liquid stream at the outlet of the transfer pump is 34.8 °C.

[0113]

Example 3

[0114] A method for treating tail gas, using the tail gas treatment system shown in Example 1, includes the following steps:

[0115] a) The tail gas stream and the jet liquid stream enter a liquid jet vacuum pump for mixing, and then enter a separator; among them, the gas in the tail gas stream includes gases containing unsaturated bonds; after the tail gas stream and the jet liquid stream are mixed, the tail gas stream cools down but does not condense;

[0116] Among them, the gas in the tail gas stream is the tail gas generated during the removal of small molecule monomers during the flash evaporation of the crude product in polyether production, including acrylonitrile, styrene and isopropanol gases; in the tail gas stream, the volume fraction of the gas containing unsaturated bonds is 7.0%; the pressure of the tail gas stream is 7 KPaA; the jet liquid stream mainly includes water, and the water content is 98.70%;

[0117] The temperature of the tail gas stream before entering the liquid jet vacuum pump is 140 °C; the mass flow ratio of the tail gas stream to the jet liquid stream is 1:1; after the tail gas stream and the jet liquid stream enter the liquid jet vacuum pump for mixing, the temperature of the tail gas stream is 45 °C.

[0118] b) A second gas stream and a second liquid stream are separated from the separator. The second gas stream is condensed, and after condensation, it is divided into a third gas stream and a third liquid stream. The third liquid stream is returned to the separator;

[0119] Among them, the separator is a sealed container; a vacuum pumping device is provided after the condenser to send the second gas stream to the condenser under negative pressure; the pressure of the separator is 18.0 KPaA;

[0120] The second gas stream is an uncondensed tail gas stream; in terms of volume percentage, the second gas stream is 37.62% water, 7.24% acrylonitrile, 12.09% isopropanol, 43.05% styrene;

[0121] In terms of mass percentage, the second liquid stream is a condensed tail gas stream; the second liquid stream is 97.75% water, 1059 PPM acrylonitrile, 2.11% isopropanol, 385 PPM styrene.

[0122] The temperatures of the third gas stream and the third liquid stream at the condenser outlet are each independently 9 °C;

[0123] By volume percentage, the third gas stream is 16.59% water, 21.13% acrylonitrile, 4.83% isopropanol, and 57.45% styrene;

[0124] By mass percentage, the third liquid stream is 37.77% water, 7.14% acrylonitrile, 12.14% isopropanol, and 42.95% styrene.

[0125] c) The second liquid stream and the third liquid stream are mixed in a separator and then sent to the inlet of a transfer pump. The fourth liquid stream at the outlet of the transfer pump is divided into two streams. One stream is sent as a jet liquid stream to a liquid jet vacuum pump, and the other stream is sent out of the system as a withdrawn stream;

[0126] Among them, the outlet pressure of the transfer pump is 0.3 MPaG; the temperature of the fourth liquid stream at the outlet of the transfer pump is 28.9 °C.

[0127]

Example 4

[0128] A method for treating tail gas, using the tail gas treatment system shown in Example 1, includes the following steps:

[0129] a) The tail gas stream and the jet liquid stream enter a liquid jet vacuum pump for mixing, and then enter a separator; among them, the gas in the tail gas stream includes gases containing unsaturated bonds; after the tail gas stream and the jet liquid stream are mixed, the tail gas stream cools down but does not condense;

[0130] Among them, the gas in the tail gas stream is the tail gas generated during the removal of small molecule monomers during the flash evaporation of the crude product in polyether production, including acrylonitrile, styrene, and isopropanol gases; in the tail gas stream, the volume fraction of the gas containing unsaturated bonds is 11.0%; the pressure of the tail gas stream is 4 KPaA; the jet liquid stream mainly includes water, and the water content is 97.30%;

[0131] The temperature of the tail gas stream before entering the liquid jet vacuum pump is 160 °C; the mass flow ratio of the tail gas stream to the jet liquid stream is 1:2; after the tail gas stream and the jet liquid stream enter the liquid jet vacuum pump for mixing, the temperature of the tail gas stream is 38 °C.

[0132] b) The second gas stream and the second liquid stream are separated from the separator. The second gas stream is condensed, and after condensation, it is divided into a third gas stream and a third liquid stream. The third liquid stream is returned to the separator;

[0133] Among them, the separator is a sealed container; a vacuum pumping device is provided after the condenser to send the second gas stream to the condenser under negative pressure; the pressure of the separator is 16.0 KPaA;

[0134] In terms of volume percentage, the second gas stream is the uncondensed tail gas stream; the second gas stream is 35.82% water, 5.11% acrylonitrile, 15.94% isopropanol, and 43.13% styrene;

[0135] In terms of mass percentage, the second liquid stream is the condensed tail gas stream; the second liquid stream is 96.92% water, 792 PPM acrylonitrile, 2.96% isopropanol, and 447 PPM styrene.

[0136] The temperatures of the third gas stream and the third liquid stream at the outlet of the condenser are each independently 13°C;

[0137] In terms of volume percentage, the third gas stream is 18.28% water, 17.25% acrylonitrile, 7.25% isopropanol, and 57.22% styrene;

[0138] In terms of mass percentage, the third liquid stream is 35.94% water, 5.03% acrylonitrile, 16.00% isopropanol, and 43.03% styrene.

[0139] c) The second liquid stream and the third liquid stream are mixed in the separator and then sent to the inlet of the transfer pump. The fourth liquid stream at the outlet of the transfer pump is divided into two streams. One stream is sent as the jet liquid stream to the liquid jet vacuum pump, and the other stream is sent out of the system as the extraction stream;

[0140] Among them, the outlet pressure of the transfer pump is 0.5 MPaG; the temperature of the fourth liquid stream at the outlet of the transfer pump is 24.0°C.

[0141]

Example 5

[0142] A method for treating tail gas, using the tail gas treatment system shown in Example 1, includes the following steps:

[0143] a) The tail gas stream and the jet liquid stream enter the liquid jet vacuum pump for mixing, and then enter the separator; among them, the gas in the tail gas stream includes gases containing unsaturated bonds; after the tail gas stream and the jet liquid stream are mixed, the tail gas stream cools down but does not condense;

[0144] Among them, the gas in the tail gas stream is the tail gas generated during the removal of small molecule monomers during the flash evaporation of the crude product in polyether production, including acrylonitrile, styrene, and isopropanol gases; in the tail gas stream, the volume percentage of the gas containing unsaturated bonds is 14.0%; the pressure of the tail gas stream is 2 KPaA; the jet liquid stream mainly includes water, and the water content is 96.1%;

[0145] The temperature of the tail gas stream before entering the liquid jet vacuum pump is 180 °C; the mass flow ratio of the tail gas stream to the jet liquid stream is 1:4; after the tail gas stream and the jet liquid stream enter the liquid jet vacuum pump and are mixed, the temperature of the tail gas stream is 27 °C.

[0146] b) Separate a second gas stream and a second liquid stream from the separator, condense the second gas stream, and after condensation, divide it into a third gas stream and a third liquid stream, and return the third liquid stream to the separator;

[0147] Among them, the separator is a sealed container; a vacuum pumping device is provided after the condenser to send the second gas stream to the condenser under negative pressure; the pressure of the separator is 13.0 KPaA;

[0148] In terms of volume percentage, the second gas stream is the uncondensed tail gas stream; the second gas stream is 33.97% water, 5.10% acrylonitrile, 12.02% isopropanol, and 48.91% styrene;

[0149] In terms of mass percentage, the second liquid stream is the condensed tail gas stream; the second liquid stream is 97.53% water, 818 PPM acrylonitrile, 2.34% isopropanol, and 493 PPM styrene.

[0150] The temperatures of the third gas stream and the third liquid stream at the outlet of the condenser are independently 16 °C;

[0151] In terms of volume percentage, the third gas stream is 20.13% water, 15.65% acrylonitrile, 5.09% isopropanol, and 59.13% styrene;

[0152] In terms of mass percentage, the third liquid stream is 34.06% water, 5.03% acrylonitrile, 12.07% isopropanol, and 48.84% styrene.

[0153] c) After the second liquid stream and the third liquid stream are mixed in the separator, they are sent to the inlet of the transfer pump. The fourth liquid stream at the outlet of the transfer pump is divided into two streams. One stream is sent as the jet liquid stream to the liquid jet vacuum pump, and the other stream is sent out of the system as the withdrawn stream;

[0154] Among them, the outlet pressure of the transfer pump is 0.7 MPaG; the temperature of the fourth liquid stream at the outlet of the transfer pump is 19.8 °C.

[0155]

Example 6

[0156] A method for treating tail gas, using the tail gas treatment system shown in Example 1, includes the following steps:

[0157] a) The tail gas stream and the jet liquid stream are mixed in a liquid jet vacuum pump and then enter a separator. Among them, the gas in the tail gas stream includes gases containing unsaturated bonds. After the tail gas stream is mixed with the jet liquid stream, the tail gas stream cools down but does not condense.

[0158] Among them, the gas in the tail gas stream is the tail gas generated during the removal of small molecule monomers during the flash evaporation of the crude product in polyether production, including acrylonitrile, styrene, and isopropanol gases. In the tail gas stream, the volume fraction of the gas containing unsaturated bonds is 17.0%. The pressure of the tail gas stream is 0.5 KPaA. The jet liquid stream mainly includes water, with a water content of 95.0%.

[0159] The temperature of the tail gas stream before entering the liquid jet vacuum pump is 200 °C. The mass flow ratio of the tail gas stream to the jet liquid stream is 1:5.5. After the tail gas stream and the jet liquid stream are mixed in the liquid jet vacuum pump, the temperature of the tail gas stream is 16 °C.

[0160] b) A second gas stream and a second liquid stream are separated from the separator. The second gas stream is condensed, and after condensation, it is divided into a third gas stream and a third liquid stream. The third liquid stream is returned to the separator.

[0161] Among them, the separator is a sealed container. A vacuum pumping device is provided after the condenser to send the second gas stream to the condenser under negative pressure. The pressure of the separator is 10.0 KPaA.

[0162] In terms of volume percentage, the second gas stream is the uncondensed tail gas stream. The second gas stream is 32.57% water, 8.93% acrylonitrile, 15.35% isopropanol, and 43.15% styrene.

[0163] The second liquid stream is the condensed tail gas stream. In terms of mass percentage, the second liquid stream is 96.62% water, 1500 PPM acrylonitrile, 3.18% isopropanol, and 502 PPM styrene.

[0164] The temperatures of the third gas stream and the third liquid stream at the outlet of the condenser are independently 20 °C.

[0165] In terms of volume percentage, the third gas stream is 18.58% water, 28.61% acrylonitrile, 7.32% isopropanol, and 45.58% styrene.

[0166] In terms of mass percentage, the third liquid stream is 32.65% water, 8.81% acrylonitrile, 15.40% isopropanol, and 43.14% styrene.

[0167] c) The second liquid stream and the third liquid stream are mixed in a separator and then sent to the inlet of a transfer pump. The fourth liquid stream at the outlet of the transfer pump is divided into two branches. One branch is sent as a jet liquid stream to a liquid jet vacuum pump, and the other branch is sent out of the system as a withdrawn stream;

[0168] Among them, the outlet pressure of the transfer pump is 0.8 MPaG; the temperature of the fourth liquid stream at the outlet of the transfer pump is 15.1 °C.

[0169]

Comparative Example 1

[0170] As Figure 2 shown, the system for treating polyether tail gas in the prior art includes: a tail gas raw material tank V1, a gas jet ejector G, a separator V2, a condenser E, and a vacuum pumping device F.

[0171] Figure 2 In it, the tail gas stream (a high-temperature gas stream containing unsaturated bonds) 101 in the tail gas raw material tank V1 is sent to the gas jet ejector G (i.e., a steam jet pump) under negative pressure. After being mixed with the steam stream 202 in the gas jet ejector G, it is sent as an ejector outlet stream 203 to the separator V2, and is separated into a fourth gas stream 204 and a fourth liquid stream; the fourth gas stream 204 is sent to the condenser E under the negative pressure generated by the vacuum pumping device F, and after condensation, it is divided into a fifth gas stream 205 and a fifth liquid stream 206; the fourth liquid stream and the cooling water stream 207 are mixed in the separator V2 to form a separator bottom discharge stream 208, and the fifth liquid stream 206 and the separator bottom discharge stream 208 converge to form another withdrawn stream 209 and are sent out of the system.

[0172] In Comparative Example 1, a gas jet ejector using externally supplied steam as the power source is adopted. Since the temperature of the steam is relatively high, the high-temperature tail gas containing unsaturated bonds is prone to self-polymerization and block the pipelines and equipment, thus affecting the long-term operation of the device, and the existing steam ejector requires a large amount of cooling water consumption.

[0173]

Comparative Example 2

[0174] It adopts a system for treating polyether tail gas similar to that in Embodiment 1 of the present invention. The difference is that the tail gas stream and the jet liquid stream are directly condensed after being mixed in the liquid jet vacuum pump, without being condensed in the condenser, and the step of recycling the third liquid material in the condenser is not carried out.

[0175] The energy consumption and water volume used in the tail gas treatment processes of the above embodiments and comparative examples are shown in Table 1.

[0176] Table 1

[0177] Example Energy consumption / KW Make-up water outside the boundary / ton Example 2 0.06 None Example 3 0.35 None Example 4 0.69 None Example 5 1.38 None Example 6 1.93 None Comparative example 1 375 30 Comparative example 2 11.50 None

[0178] The present invention has been described in detail in connection with specific embodiments and exemplary examples, but these descriptions should not be construed as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications or improvements can be made to the technical solutions of the present invention and their implementation manners, and all of these fall within the scope of the present invention. The protection scope of the present invention shall be subject to the appended claims.

[0179] All publications, patent applications, patents and other references mentioned in this specification are hereby incorporated by reference in their entirety. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0180] When this specification uses prefixes such as "known to those skilled in the art", "prior art" or similar terms to introduce materials, substances, methods, steps, devices or components, etc., the objects introduced by such prefixes cover those commonly used in the art at the time when this application is filed, but also include those that are not commonly used at present but will become recognized in the art as suitable for similar purposes.

[0181] In the context of this specification, any matter or thing not mentioned, except as expressly stated, shall directly apply those known in the art without any change.

Claims

1. A method for tail gas treatment, comprising the following steps: a) Mix the tail gas stream and the jet liquid stream in a liquid jet vacuum pump, and then enter a separator; wherein, the gas in the tail gas stream includes a gas containing an unsaturated bond; after the tail gas stream is mixed with the jet liquid stream, the tail gas stream is cooled but not condensed; b) Separate a second gas stream and a second liquid stream from the separator, condense the second gas stream, and after condensation, divide it into a third gas stream and a third liquid stream, and return the third liquid stream to the separator; c) Mix the second liquid stream and the third liquid stream in the separator and send them to the inlet of a transfer pump. The fourth liquid stream at the outlet of the transfer pump is divided into two streams, one stream is sent as the jet liquid stream to the liquid jet vacuum pump, and the other stream is sent out of the system as a withdrawn stream.

2. The method for tail gas treatment according to claim 1, characterized in that: In step a), the unsaturated bond in the gas containing an unsaturated bond refers to C=C, or / and C≡C, or / and C≡N; preferably, the gas in the tail gas stream includes acrylonitrile, or / and styrene, or / and isopropanol gas; preferably, in the tail gas stream, the volume percentage of the gas containing an unsaturated bond is 2.0% - 18.0%, preferably 3.0% - 17.0%; and / or, the pressure of the tail gas stream is 0.1 - 15.0 KPaA, preferably 0.1 - 12 KPaA; more preferably 0.1 - 10.0 KPaA; and / or, the jet liquid stream mainly includes water, preferably the mass content of water is 94.0% - 99.9%, more preferably 95.0% - 99.9%.

3. The method for tail gas treatment according to claim 1, characterized in that: In step a), the temperature of the tail gas stream before entering the liquid jet vacuum pump is 110 - 210 °C, preferably 120 - 200 °C; and / or, the mass flow ratio of the tail gas stream to the jet liquid stream is 1:(0.1 - 6.0), preferably 1:(0.15 - 5.5); more preferably, after the tail gas stream and the jet liquid stream are mixed in the liquid jet vacuum pump, the temperature of the tail gas stream is 10 - 60 °C, preferably 10 - 55 °C, more preferably 15 - 55 °C.

4. The method for tail gas treatment according to claim 1, characterized in that: In step b), the separator is a sealed container, and a vacuum pumping device is provided after the condenser used for condensation. The vacuum pumping device sends the second gas stream to the condenser under negative pressure; Preferably, the pressure in the separator is 10.0 - 30.0 KPaA, preferably 10.0 - 25.0 KPaA; more preferably 10.0 - 20.0 KPaA.

5. The method for tail gas treatment according to claim 1, characterized in that: In step b), the second gas stream is an uncondensed tail gas stream; preferably, by volume percentage, the second gas stream includes 28.00% - 48.00% water, 1.20% - 9.20% acrylonitrile, 2.70% - 22.70% isopropanol, 24.40% - 44.40% styrene; and / or, The second liquid stream is a condensed tail gas stream; preferably by mass percentage, the second liquid stream comprises 91.00% - 99.90% water, 10 - 4000 PPM acrylonitrile, 0.02% - 5.00% isopropanol, and 1 - 2000 PPM styrene.

6. The method for treating tail gas according to claim 1, wherein: step b), the temperatures of the third gas stream and the third liquid stream at the condenser outlet are each independently ≤ 40°C, preferably ≤ 20°C; Preferably, by volume percentage, the third gas stream comprises 7.00% - 27.00% water, 5.81% - 30.00% acrylonitrile, 0.10 - 10.10% isopropanol, 41.80% - 81.80% styrene; and / or, by mass percentage, the third liquid stream comprises 27.70 - 47.70% water, 0.10 - 10.20% acrylonitrile, 2.50 - 23.40% isopropanol, 24.00 - 68.40% styrene.

7. The method for treating tail gas according to claim 1, wherein: step c), the outlet pressure of the transfer pump is 0.2 - 1.0 MPaG, preferably 0.2 - 0.8 MPaG; and / or, the temperature of the fourth liquid stream at the outlet of the transfer pump is 15 - 40°C, preferably 15 - 35°C.

8. A system for treating tail gas, comprising: a tail gas raw material tank, a liquid jet vacuum pump, a separator, a condenser, a transfer pump, and a vacuum pumping device; the outlet of the tail gas raw material tank is connected to the gas inlet of the liquid jet vacuum pump; the outlet of the transfer pump is connected to the liquid inlet of the liquid jet vacuum pump; the outlet of the liquid jet vacuum pump is connected to the inlet of the separator; the liquid outlet of the separator is connected to the inlet of the transfer pump; the gas outlet of the separator is connected to the inlet of the condenser; the liquid outlet of the condenser is connected to another inlet of the condenser; the vacuum pumping device is connected to the gas material flow pipeline of the condenser; the outlet of the transfer pump is also connected to the material extraction pipeline; Preferably, the system adopts the method for treating tail gas according to any one of claims 1 - 7.

9. The system for treating tail gas according to claim 8, wherein: the tail gas raw material tank is selected from a vacuum container, preferably a stirring device is provided in the vacuum container; and / or, the liquid jet vacuum pump is an ejector with a Venturi structure; and / or, the transfer pump is selected from at least one of a booster pump and a centrifugal pump.

10. The system for treating tail gas according to claim 8, wherein: the outlet of the liquid jet vacuum pump is located inside the separator, and the outlet of the liquid jet vacuum pump is higher than the maximum height of the liquid level inside the separator.

11. Application of the method for treating tail gas according to any one of claims 1 - 7 or the system for treating tail gas according to any one of claims 8 - 10 in the treatment of tail gas in polyether production.

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